1. Field of the Invention
The present invention relates to a producing method of a flexible wired circuit board and, more particularly, to a method of producing a flexible wired circuit board, while an elongate substrate is conveyed using rolls.
2. Description of the Prior Art
The method of forming a conductive pattern on a surface of an elongate substrate of a polyimide sheet or the like, while the elongate substrate is conveyed using rolls, for improvement in production efficiency of the flexible wired circuit board, is known.
Along with the trend toward lighter, thinner, and more compact electronic components, the trend in flexible wired circuit boards is also toward thinner profile. A thin, elongate, substrate is however apt to be creased or get wrinkled when conveyed using rolls. To prevent this, for example JP Laid-open (Unexamined) Patent Publication No. Hei 6-132628 proposes that a carrier film, such as a polyethylene terephthalate film, is bonded to a surface of a thin, copper clad laminate.
Meanwhile, along with improvements in a fine conductive pattern in recent years, attention has been attracted of a semi-additive process to form the conductive pattern by electrolysis plating. When the conductive pattern is formed by the electrolysis plating, the following problems occur with the above-said flexible wired circuit board with the carrier sheet bonded to the elongate substrate, however.
In general, in the electrolysis plating, a current density becomes higher at both widthwise end portions of the elongate substrate than at a central portion of the same. As a result, thickness of the conductive pattern plated becomes larger at the both widthwise ends of the elongate substrate than at the central portion of the same. When the elongate substrate is rolled up after the electrolysis plating, differences in thickness between the both end portions of the elongate substrate and the central portion of the same are accumulated. As a result of this, the elongate substrate is undulated and deformed plastically at the both widthwise end portions by the wind-up pressure, causing the bonded carrier sheet to be stripped off from the elongate substrate at the both end portions thereof.
This may in turn cause the problem that in the process subsequent to the conductive pattern forming process, etching solution or developing solution is entrained into a gap between the carrier sheet and the elongate substrate at both end portions thereof formed by the strip of the carrier sheet from the elongate substrate via the capillary phenomenon. Then, the entrained solution remains through the subsequent processes, causing contamination of the flexible wired circuit board obtained.